VG02118 White Blister

This project details the outcomes of a 12-month scoping study on white blister (rust) on brassicas which investigated the identification of the Albugo candida race causing the epidemic, the source of the epidemic and management practices for white blister in the field.

White blister is a fungal disease of broccoli and cauliflower, which devastated Victorian crops during the summer of 2001-02. Within eighteen months it had spread to broccoli and cauliflower crops across the whole of southern Australia. It produces unsightly white blisters and swellings on the leaves and heads. Crops can be totally affected causing up to 100% losses to the grower.

Although white blister has previously been reported in Australia on these plants, it has not been associated with epidemics. Researchers at DPI Knoxfield conducted trials to identify the race of the fungus causing the disease, the chemicals required to control it and the possible source of the epidemic. AUSVEG, HAL and the Victorian government supported this work.

Authors

Liz Minchinton

Robert Faggian

Joanna Petkowski

Craig Murdoch

Fiona Thomson

Savitri Nadesan

Worldwide there are over 10 different races of white blister, which are largely specific to certain plant hosts. The race of the fungus responsible for this epidemic is similar to the established race 9 of white blister found overseas, which infects broccoli, cauliflower, cabbage and Brussels sprouts, but differs in that it does not infect cabbage. A more rapid DNA fingerprinting approach is being evaluated to speed up tests and improve detection.

Fungicide sprays for white blister were evaluated in three field trials. A total of 17 systemic, contact and soft chemicals (those with short or no withholding periods) were identified, which controlled the disease by up to 100%. It is imperative to rotate chemicals from different fungicide groups as white blister can quickly form resistance to fungicides.

The source of the white blister infection is a contentious issue. Seed does not appear to be a consistent source of white blister as no spores were detected in a seed wash of 25,000 seeds from the cultivar Greenbelt. The only evidence of seed-borne infections were the spore-containing galls found on seedlings early in the epidemic.

The researchers acknowledge the financial support for this project from Horticulture Australia Limited (HAL), AUSVEG, the Federal Government and the Department of Primary Industries, Primary Industries Research Victoria.

The authors thank the the members of the advisory groups, Daniel Gleeson, James Kelly, Kon Koroneos, David McDonald, Mark Milligan, Rob Nave, Matt Newland, Dale O�Connell, Karl Riedel and Ian Willert for their valuable contribution to this project.